Electric resistor



Jan. 3, 1956 KQENIG 2,729,728

ELECTRIC RESISTOR Filed Sept. 21 1953 INVENTOR Heme/v 61 Kaemy UnitedStates Patent ELECTRIC RESISTOR Herbert G. Koenig, Merriam,Manufacturing Company, ship Kans., assignor to Trio Griggsville, Ill., apartner- This invention relates to improvements in electricalinstruments, and particularly to devices such as potentiometers,rheostats and the like, wherein it is desired to rotate the relativelyengaging conductive parts more than 360 degrees.

It is the most important object of the present invention to provide anelectrical control having a conductive brush and a conductive band,interengageable and relatively rotatable, the brush being shiftable morethan 360 degrees while remaining in contact with the band because of theprovision of a notch within the instrument body adapted to receive oneend of the brush.

Another object of the present invention is to provide a brush-typedevice, wherein the brush itself is in wiping engagement with a spiralconductive band mounted on an inner Wall of the same configuration,there being a tongue within the body of the instrument presenting anotch into which the brush is adapted to engage.

Other objects include important details of construction, all of whichwill be made clear as the following specification progresses.

In the drawing:

Figure 1 is a top plan view of ing rotatable control made vention.

Fig. 2 is a cross-sectional view taken on line II-II of Fig. 1.

Fig. 3 is a cross-sectional view taken on irregular line IlL-III of Fig.2 looking in the direction of the arrows.

Fig. 4 is an enlarged fragmentary view similar to Fig. 3 illustratingthe position of the brush at one end of its path of travel, and

Fig. 5 is a view similar to Fig. 4 showing the brush at the opposite endof its path of travel, after having moved more than 360 degrees.

The electrical instrument embodying the principles of the presentinvention may take many different forms but for the most part it iscontemplated that the same consist of variable resistors such aspotentiometers, rheostats and the like, normally adapted for mountingupon an in strurnent panel 10. In the form of my invention shown forillustration, a body broadly designated by the numeral 12, is hollow andincludes a top wall 14, a preferably cylindrical side wall 16 and aremovable closure cap 18. Wall 14 has a threaded stud 20 extendingthrough the panel and held in place thereon by a nut 22, there being adial 24 interposed between nut 22 and one face of panel 1i and suitablycalibrated as at 26. The inner face 28 of the wall 16 is spiral,presenting a notch 30 and an overhanging tongue 32 defining the notch30. Face 28 receives a similarly shaped conductive band 34 that extendsfrom one end thereof within the notch 30 throughout the length of theface 28 and terminates in overlapped relationship to the tongue 32. Thespiral band 34 is suitably afiixed to the face 28 within the hollow body12 and may be coupled within an electric circuit by a conductor meanssuch as wires 36 and 38 joined to the band 34 at the ends thereof.

an electrical device havpursuant to the present in- The stud 20rotatably receives a spindle 40 having an indicator knob 42 on theoutermost end thereof. A brush 44 of resilient material has a wipingbutton 46 on the outermost free end thereof in sliding engagement withthe innermost face of band 34. Brush 44 is riveted or otherwise afiixedat its opposite end as at 47, to radial arm 48 secured to the spindle 40by a screw 50. Detent 52 on the arm 48 is in wiping engagement withconductor ring 54 imbedded within the innermost face of wall 14.Electrical contact is made with the ring 54 by means of a wire 56. It isunderstood, of course, that band 34, brush 44, arm 48 and ring 54 areall of conductive material. Accordingly it is desired that the body 12be of insulating material or the conductive elements otherwise insulatedfrom the knob 42 and the panel 10.

In operation, when the brush 44 is at one end of its path of travel,button 46 is disposed within the notch 30 beneath the finger 32 andbetween the relatively overlapping ends of the band 34, all as shown inFigs. 3 and 4 of the drawing. When the brush 44 is rotated relative tothe band 34 to the opposite end of its path of travel by manipulation ofpointer knob 42, it will have traveled more than 360 degrees dependingupon the length of the finger 32 or the depth of notch 30 and when thebutton 46 is at said opposite end of its path of travel it engages theopposite end of band 34 in overlying relationship to the finger 32.

Those skilled in this field will appreciate the advantages emanatingfrom a construction permitting rotation of a wiping element in more thana complete circle, and it is to be seen that the construction hereincontemplated permits such operation without adversely affecting thenormal functions of the instrument. Such construction is simple,inexpensive and easily manufactured, and while details of constructionmay vary within the spirit of the invention it is desired to be limitedonly by the scope of the appended claims.

Having thus described the invention what is claimed as new and desiredto be secured by Letters Patent is:

1. In an electrical instrument, a hollow body; a conductive brush in thebody; means interconnecting the brush and the body for relativerotation; a spiral conductive band in the body, the brush being inwiping engagement with the band; and conductor lines coupled with theband and the brush, said band having a pair of relatively overlappingends, spaced to receive a portion of the brush therebetween, whereby torender the band and the brush relatively rotatable for more than 360degrees while the brush remains in engagement with the band, said bodybeing provided with a spiral, radially inward facing wall, the bandbeing secured to the radially inward face of said wall.

2. In an electrical instrument, a hollow body; a conduc tive brush inthe body; means interconnecting the brush and the body for relativerotation; a spiral conductive band in the body, the brush being inwiping engagement with the band; and conductor lines coupled with theband and the brush, said band having a pair of relatively overlappingends, spaced to receive a portion of the brush therebetween, whereby torender the band and the brush relatively rotatable for more than 360degrees while the brush remains in engagement with the band, said bodybeing provided with a spiral, radially inward facing wall, the bandbeing secured to the radially inward face of said wall, there being anotch in said body, one end of the wall face and one end of the bandterminating in said notch, said body having a tongue at the opposite endof the wall face and spaced from said one end of the wall face topresent said notch, the brush having a portion adapted to extend intothe notch between the tongue and said one end of the band.

3. In an electrical instrument, a hollow body; a conr r 3 debatebrush'in the body; mean interconnecting the brush and the body for relativerotation; a spiral conductive band in the body, the brush being inwiping engagement with the band, and conductor lines coupled withjheband and the brush, said band having a pair of one end of the' wall faceand one end of the band termimating in said notch, saidbody having atongue at the opposite end of the wall face and spaced from said onee'nd'of the wallface to present said notch, the brush hav-' mg avportion adapted to extend into the notch between the tongue and said one endof the band, the opposite end of the band overlapping the tongue,whereby the bandzand' the wall face are coextensive in length.

4. In an electrical instrument, a. housing having an interior-chamber, aconductive brush mounted for rotation within the chamber upon a pivotdefining an axis, a spiral resistance element mounted in the chamber andhaving theen ds thereof spaced radially apart to form radially inneroverlapping portion, and a radially outer uifderlapping portion, meansinsulating the overlapping and underlapping portions one from the othercomprising a tongue generally arcuate about said axis substantially vco-extensive with said overlapping portion and forming an arcuate notchwith said underlappingportion, said brush comprising a metallic striphaving one end secured to saidpivot and the opposite end free to engageagainst and in electrical wiping contact with said element, said stripbeing resilient and biased to exert radially outward pressure againstsaid element, and arranged to ride upon said spiral element uponrotation of said pivot.

5; A combination as described in claim 4 in which the a free end of saidstrip has a portion arcuate about said axis whereby to be disposedparallel with said element and enabled thereby to enter said notchWithout engaging said tongue or overlapping portion.

6. A combination as described in claim 4 in which the element isconnected to at least one conducting lead, said housing is provided witha circular conducting element insulated from said resistance element andconnected to a second conducting lead, and means are provided onsaid'brush for electrically engaging with said circular conductingelement during rotation thereof.

7. An electrical device of the character described, comprising a housinghaving an interior chamber of gen-t erally cylindrical formation, an armpivotally, mounted on the housing within the chamber for rotation on anaxis in the centefof'the' chamber, the inwardly exposed chamber wallface being spiralled about said axis and having an end overlapping theother by an amount substantially less than a single revolution andradially spaced therefrom, the housing having an extension supportingthe overlapping end and providing thereby a recess alongside theoverlapped end, a fiat resistance element strip secured to the said wallface along the length thereof and following the spiral, the ends of theresistance element being insulated one from the other and from said arm,a resilient conductive wiper mounted on the arm for rotation therewithand having a contact at its free end engaging and riding upon theresistance element, the wiper being biased to press against theresistance element, the path defined by the wiper during rotation beingsubstantially contained within the volume encompassed by said strip andplanes normal to said axis spaced therealong and containing the axiallyspaced edges of said strip.

8. A device as described in claim 7 in which the free end of the wiperis arc'uately bent to ride substantially parallel with said strip whenengaged thereagainst, and thewiper is arrangedto move the bend into therecess when rotated on one direction, with the bend and wiperelectrically insulated from the overlapping end while the contactengages the overlapped end. 7

9. An electrical device of the character described, comprising ahousing, having an interior chamber of generally cylindrical formation,an arm pivotally mounted on the housing within the chamber for rotationon an axis in the center of the chamber, the inwardly exposed chamberwall face being spiralled about said axis and having an end overlappingthe other by an amount substantially less than a single revolution,radially spaced and insulated therefrom and providing a recess alongsidethe overlapped end, a fiat resistance element strip secured to the saidwall face along the length thereof following the spiral with the ends ofthe said resistance element insulated one from the other and from saidarm, a resilient conductive wiper mounted on the arm for rotationtherewith and having a contact at its free. end engaging and riding uponthe resistance element, said wiper being secured to said arm at a pointspaced substantially radially of said axis whereby the angle defined bya line between said point of securement and axis and the wiper is anacute angle.

References Cited'in the file of this patent UNITED STATES PATENTS1,785,779 Laut'er Dec. 23, 1930

